MyBatis first-level cache detailed explanation: How to improve data access efficiency?

During the development process, efficient data access has always been one of the focuses of programmers. For persistence layer frameworks like MyBatis, caching is one of the key methods to improve data access efficiency. MyBatis provides two caching mechanisms: first-level cache and second-level cache. The first-level cache is enabled by default. This article will introduce the mechanism of MyBatis first-level cache in detail and provide specific code examples to help readers better understand how to use first-level cache to improve data access efficiency.

What is the first level cache?

The first-level cache means that when performing a query operation in the same SqlSession, MyBatis will cache the query results. The next time the same query operation is performed, the results will be obtained directly from the cache without the need for Then initiate a query request to the database. This can reduce the number of database accesses and improve data query efficiency.

The scope of the first-level cache

The scope of the first-level cache is the operations in the same SqlSession, that is, the query operations executed in the same SqlSession will share the same cache.

The life cycle of the first-level cache

The life cycle of the first-level cache follows the life cycle of SqlSession. When a SqlSession is closed, the first-level cache is also cleared. If developers need to share the first-level cache between multiple queries, they can do this by keeping the SqlSession persistent or manually clearing the cache.

Usage example of first-level cache

Next we will demonstrate the use of first-level cache through a specific code example.

1. First, define a query method in the Mapper interface of MyBatis:

public interface UserMapper {
    User selectUserById(int id);
}

2. Then, write the SQL query statement in the corresponding Mapper XML file:

<select id="selectUserById" resultType="User">
    SELECT * FROM user WHERE id = #{id}
</select>

3. Next, perform the query operation in the code and use the first-level cache:

SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
SqlSession sqlSession = sqlSessionFactory.openSession();
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

// 第一次查詢，會向數(shù)據(jù)庫發(fā)起查詢請求
User user1 = userMapper.selectUserById(1);
System.out.println("第一次查詢結(jié)果：" + user1);

// 第二次查詢，不會向數(shù)據(jù)庫發(fā)起查詢請求，直接從緩存中獲取
User user2 = userMapper.selectUserById(1);
System.out.println("第二次查詢結(jié)果：" + user2);

sqlSession.close();

In the above code example, the first query will A real query request is initiated to the database, and when the same data is queried for the second time, because the first-level cache is hit, the query request will not be initiated to the database again, but the results will be obtained directly from the cache. This can improve data access efficiency and reduce database access pressure.

How to use first-level cache to improve data access efficiency?

• Try to keep the SqlSession short and avoid opening the SqlSession for a long time to avoid the first-level cache causing data to expire or occupying too much memory.
• Reasonable use of SqlSession's clearCache() method to manually clear the cache can clear the cache at the appropriate time and ensure the validity of the cached data.
• Avoid sharing the same SqlSession instance in a multi-threaded environment, which may cause data inconsistency.

In general, MyBatis first-level cache is a very effective mechanism to improve data access efficiency. Proper use of first-level cache can reduce the number of database accesses and improve system performance. However, when using the first-level cache, developers need to pay attention to the life cycle and scope of the cache and how to avoid potential problems caused by the cache to ensure the stability and reliability of the system.

This article introduces the mechanism of MyBatis first-level cache in detail, provides specific code examples, and gives some suggestions for using first-level cache to improve data access efficiency. I hope readers can better understand it through the introduction of this article. Understand and apply first-level caching to improve your data access efficiency.

Conclusion

Through the introduction of this article, I hope readers can have a deeper understanding of MyBatis's first-level cache and master how to use the first-level cache to improve data access efficiency. At the same time, it is recommended that readers practice more in actual projects and rationally use the first-level cache in combination with specific scenarios to achieve higher system performance and user experience. I wish readers better results in data access!

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